The present invention relates to mechanical assemblies, particularly bearing assemblies, incorporating sensing means for sensing positional relationships or motion.
Bearing or mechanical assemblies which employ electromagnetic tachogenerators are know per se. In one form of known assembly a stationary coil has a current induced therein by rotating magnets. To achieve a reasonable signal to noise ratio the coil requires a large number of turns and this is disadvantageous primarily since sufficient space to accommodate the coil needs to be provided. Hitherto it has also been generally difficult to provide a reliable speed-indicative signal which is accurate in the low to zero speed range. Where a tachogenerator is used to sense the speed of a shaft it is known to employ an additional drive means coupled to the end of the shaft to step up the rotary motion but this leads to an expensive and bulky construction. Otherwise a magnetic projection can be attached to the shaft and the tachogenerator is then carried on a special mounting such as an outrigger bracket. It is known to construct a bearing assembly incorporating a tachogenerator but strong magnetic fields in or near bearings are generally undesirable since metallic particles will tend to be attracted to the bearing. Known assemblies are often bulky and complex and there is a need for simpler constructions in which standard units, such as rotary bearings, can be adopted without extensive modification.